Gelled ammonium nitrate-nitroethane explosive composition



United States Patent Oil 3,377,218 GELLED AMMONIUM NITRATE-NITROETHANE EXPLOSIVE COMPOSITION Robert A. Brown, Marion, Ill., assignor to Commercial Solvents Corporation, New York, N.Y., a corporation of Maryland No Drawing. Filed Dec. 12, 1966, Ser. No. 600,786

a 6 Claims. (Cl. 149-50) ABSTRACT OF THE DISCLOSURE This invention relates toexplosive compositions con taining ammonium nitrate and nitroethane. In a particular aspect this invention relates to non-cap-sensitive explosive compositions in gelled form having high rates of detonation. In a further aspect this invention relates to non-cap-sensi-tive explosive compositions in gelled form having high rates of detonation useful in the seismic exploration for oil and natural gas found beneath the ocean floor.

1 Explosivestare used in the seismic exploration for oil and natural gas deposits found beneath the ocean floor. Energy from shock waves produced by the detonation of explosives beneath the surface of the Water travels downward to beneath the ocean floor and is then partially reflected upward. The energy returning to the surface is picked up by a receiving apparatus known as a geophone, which in turn transmits the received impulses to amplify ing and recording devices. Interpretation of the recorded information permits the skilled geophysicist to determine geological structures where oil and natural gas are likely to have accumulated.

Explosive compositions used in marine seismic petro leum exploration desirably have high rates of detona tion. Because of the stringent safety requirements in .major ports regarding the loading of explosives on ocean going vessels, such explosives must also be non-cap-sensitive; that is, incapable of detonation by a single No. 8 electric blasting cap.

Explosive compositions in gelled form comprising ammonium nitrate, nitroparafins such as nitromethane, nitroethane and nitropropane and a gelling agent for the nitroparafiins are known to the art and have a wide variety of applications. Prior explosive compositions containing ammonium nitrate and nitroparaflins in gelled form have not been suitable for use in marine seismic exploration because of failure of the compositions to meet the requirements outlined above.

It is an object of the present invention to provide noncap-sensitive explosive compositions in gelled form having high rates of detonation containing ammonium nitrate and nitroethane.

It is a further object of the present invention to provide non-cap-sensitive explosive compositions containing ammonium nitrate and nitroethane in gelled form having high rates of detonation useful in marine seismic exploration for oil and natural gas.

Other objects and advantages of the present invention 3,377,218 Patented Apr. 9, 1968 ice will be apparent from the specification and appended claims.

The present invention resides in the discovery that non-cap-sensitive explosive compositions having high rates of detonation are prepared by forming an intimate admixture of ammonium nitrate of particle size sufliciently small to substantially completely pass through a IO-mesh screen with not more than 22% passing through a 200- mesh screen, nitroethane, and a gelling agent for the nitroethane wherein the weight ratio of ammonium nitrate to nitroethane is in the range of from about :25 to about 85:15.

In the present application the terms rate of detonation and detonation rate are used interchangeably with the term detonation velocity. The rate of detonation of an explosive is the rate at which the detonation front passes through the explosive material. Detonation rate is typically expressed in feet per second. For the purpose of the present invention high detonation rates are generally considered to be in excess of 12,000 feet per second. The compositions of the present invention have detonation rates in excess of 12,000 feet per second with detonation rates of in excess of 15,000 feet per second being reasonably common in freshly prepared material; that-is, material prepared within the most recent 24-hour period.

Any suitable gelling agent for thickening or gelling the normally liquid nitroethane may be employed in the compositions of the present invention. Examples of such gelling agents include nitrocellulose, ethyl cellulose, cellulose acetate, cellulose acetate butyra-te, polyoxyethylene having molecular weights in the range of from about one hundred thousand to about five million and the like. Because of the excellent results obtained therewith, nitrocellulose is preferred as the gelling agent.

The amount of gelling agent suitable for main the explosive compositions of the present invention will vary, depending principallyon the particular gelling agent employed and on the viscosity desired for each particular composition. Typically, amounts in the range of from about 2 to about 15% by weight of gelling agent based on the weight of the nitroethane are employed. Preferred amounts are in the range of from about 5 to about 10% by weight.

The weight ratio of ammonium nitrate to nitroethane is a critical feature of the present invention and, as previously stated, must be in the range of from about 75:25 to about 85:15. Preferably, the Weight ratio of ammonium nitrate to nitroethane is about :20.

The particle size of the ammonium nitrate is also a critical feature of the present invention and, as previously stated, the ammonium nitrate must be of particle size sufiicient to substantially completely pass through a 10- mesh screen with not more than 22% by weight passing through a 200-mesh screen. The particle size distribution is preferably as follows:

Screen Size Percentage (U.S. Sieve Series) Minimum Maximum Any suitable form of ammonium nitrate may be used in the compositions of the present invention provided, of course, the particle size limitation is observed. Fertilizer grade and explosive grade ammonium nitrates are suitable. For example, granular ammonium nitrate and ground ammonium nitrate prills may be employed. The ammonium nitrate may be uncoated or coated. Coatings for ammonium nitrate are well known to the art and include diatomaceous earth, wax, kaolin clay and the like.

The explosive compositions of the present invention are prepared by forming an intimate admixture of ammonium nitrate, nitroethane and gelling agent in the amounts and ratios set forth above. The mixing may be carried out by any suitable procedure using mixing equipment suitable for mixing the ingredients. The intimate admixtures have the consistency of heavy doughs and may be termed gels. The compositions may be formed by first mixing the nitroethane and gelling agent to form a thickened or gelled nitroethane composition and subsequently mixing the gelled composition with the ammonium nitrate. As an alternate procedure, the ammonium nitrate, nitroethane and gelling agent may be placed in mixing equipment and mixed in a one-step operation.

By way of example, 800 lbs. of ground ammonium nitrate of particle size sufficiently small to substantially completely pass through a IO-mesh screen with not more than 22% passing through a 200-mesh screen prepared by grinding fertilizer grade, high density, ammonium nitrate prills, 200 lbs. of nitroethane and 15 lbs. of nitrocellulose are placed in a mixing machine and the mixer is operated until an intimate admixture is formed. After thorough mixing the admixture may be packaged in any desired quantities. By way of example, the mixture is passed to a hopper and there fed in 50-lb. quantities or other desired quantities into appropriately sized Water resistant containers. The loaded container is then equipped with a detonating device, as for example, a primer, of sufiicient power to detonate the explosive composition contained therein. The containers can be formed of any suitable container material. Waterproof or water resistant containers are naturally preferred. Typical container materials include polyethylene, polyvinyl chloride, polystyrene, fibrous materials such as wood, paper and cardboard; ferrous metals and non-ferrous metals such as tin, copper and aluminum, The packaged explosive composition is suitable for detonation under water in the seismic exploration for oil and natural gas. The packaged explosive composition has a detonation rate of in excess of 12,000 feet per second and is non-cap-sensitive.

From the foregoing those skilled in the art should readily understand that the present invention provides explosive compositions which are well adapted for uses 4 requiring non-cap-sensitive gelled explosive compositions having high rates of detonation.

Since many embodiments of this invention may be made and since many changes may be made in the embodiments described, the foregoing is to be interpreted as illustrative only and the invention is defined by the claims appended hereto.

I claim:

1. A non-cap-sensitive explosive composition in gelled form having a high detonation rate consisting essentially of an intimate admixture of ammonium nitrate of particle size sufficiently small to substantially completely pass through a 10-mesh screen, not more than 22% by weight of said ammonium nitrate passing a ZOO-mesh screen, nitroethane and gelling agent for the nitroethane, the weight ratio of ammonium nitrate to nitroethane being in the range of from about :25 to about :15 and the amount of gelling agent being sufficient to etfectively thicken said mixture.

2. The composition of claim 1 wherein the weight ratio of ammonium nitrate to nitroethane is about 80:20.

3. The composition of claim 1 wherein the amount of gelling agent is in the range of from about 2 to about 15% by weight based on the weight of the nitroethane.

4. The composition of claim 3 wherein the amount of gelling agent is in the range of from about 5 to about 10% by weight based on the weight of the nitroethane.

5. The composition of claim 1 wherein the gelling agent is nitrocellulose.

6. The composition of claim 1 wherein the ammonium nitrate is of particle size distribution to be partially retained on screens of 35, 60 and mesh.

References Cited UNITED STATES PATENTS 1,113,275 10/1914 Woodbury 149-112 X 3,133,844 5/1964 Royer et al. 149-89 X 3,318,741 5/1967 Jones 149-89 CARL D. QUARFORTH, Primary Examiner. L. DEWAYNE RUTLEDGE, Examiner. S. J. LECHERT, 111., Assistant Examiner. 

